WG2: Characterisation of HIPP plasmas and coatings

Within the Action plasma measurement and characterisation will be a key theme. Since HIPP processes are characterised by high plasma densities and high ionised particle fluxes to the growing film in the ion-assisted deposition process, characterisation of the plasmas and processes is essential for understanding and improvement. For instance, a range of complementary electrical and optical diagnostics techniques will be developed across institutes to facilitate better, more accurate determination of the key plasma parameters in high density plasma processing. In particular, the relationship between the spatial and temporal dynamics of the ionic, neutral, and radical species (in reactive plasmas) has to be understood. This information is deficient, especially in the case of pulsed plasma deposition methods.

For electric diagnostics tools, the workhorse is the Langmuir probe, which provides, localised plasma density, temperature and potential information. There should be a drive to provide better, more sophisticated electrical probes, such as the ion flux sensors and monitors that can yield the ion flux density measurements during the process, a critical factor in deposition. They can operate even when deposited upon during the process up to several micrometer thick layers. They should be flush-mounted in the substrate to avoid pertubating the plasma. Emissive probes will be designed to determine better potential distributions that determine the bombarding ion energy at the substrate. One huge area of importance is the development of time and energy resolved mass spectroscopic techniques for direct particle sampling from the plasma. These tools are planned to be designed to work in conjunction with electrical probes to gain better overview of the plasma and plasma-substrate interface processes. The tools described can be applied to a range of techniques used to yield high ionisation plasma as described above. Especially in the pulsed methods, a better time resolution capabilities for mass-spectrometric measurements is essential.

One great possibility for an Action like this is to work towards developing a standard reactor, with a complete suite of diagnostic tools for direct comparison between different techniques. For instance, separate institutes with pertinent skills may develop different non-invasive techniques such as line of sight passive optical emission spectroscopy, point-wise active Laser induced fluorescence, and even Thompson scattering to determine plasma concentrations and energetic and these could be benchmarked against invasive electrical techniques. Therefore WG2 will provide selected and well suited characterisation methods and tools for comprehension and tailoring HIPP plasmas.